Processes of continuous chemical nickel plating



Jlm 13, 1967 p TALMEY ET AL PROGESSES OF CONTINUOUS CHEMICAL NICKEL PLATING Filed. April 9, 195e w L J TNYIA N# mwm TMIA w SG L 5&7/ .www .Sb SQ @w d umm IA IA m m QN QMN ,B Nb GNN KMU N Y j L MUM@ Mm@ MUR Mmmm. mmm WMU E b. vv MMW Nv mv N N E $5: kum l@ Q5 Q w U .lm X Km (m Mm fwn cm @m IN VEN TOR. Paal a/mey, Graa/'fe (5a/ze# By 00m/a E Meme/7] United States Patent O 3,325,297 PRGCESSES 0F CONTINUUS CHEMICAL NICKEL PLATlNG Paul Talmey, Barrington, Ill., and Gregoire Gutzeit, Highland, and Donald E. Metheny, Hammond, Ind., as-

signors to General American Transportation Corporation, Chicago, Ill., a corporation of New York Filed Apr. 9, 1956, Ser. No. 576,931 23 Claims. (Cl. 106-1) This application is a continuation-in-part of the copending application of Paul Talmey, Gregoire Gutzeit and Donald E. Metheny, Ser. No. 479,040, led Dec. 31, 1954, now abandoned.

The present invention relates to processes of continuous chemical nickel plating of catalytic materials; and it is the general object of the invention to provide an improved process of the general character of that disclosed in U.S. Patent No. 2,717,218, granted on Sept. 6, 1955 to Paul Talmey and William l. Crehan.

The chemical nickel plating of a catalytic material employing an aqueous bath of the nickel cation hypophosphite anion type is based upon the catalytic reduction of nickel cations to metallic nickel and the corresponding oxidation of hypophosphite anions to phosphite anions with the evolution of hydrogen gas at the catalytic surface. The reactions take place when the body of catalytic material is immersed in the plating bath, and the exterior surface of the body of catalytic material is coated with nickel. The following elements are catalytic for the oxidation of hypophosphite anions and thus may be directly nickel plated: iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The following elements are examples of materials lwhich may be nickel plated by virtue of an initial displacement deposition of nickel thereon either directly or through a galvanic effect: copper, silver, gold, beryllium, germanium, aluminum, carbon, vanadium, molybdenum, tungsten, chromium, selenium, titanium and uranium. The following elements are examples of noncata'lytic materials which ordinarily may not be nickel plated: bismuth, cadmium, tin, lead and zinc. The activity of the catalytic materials varies considerably and the following elements are particularly good catalysts in the chemical nickel plating bath: iron, cobalt, nickel andpalladium. The chemical nickel plating process is autocatalytic since both the original surface of the body being plated and the nickel. metal that is deposited on the surface thereof are catalytic. As time proceeds, the anions, as contrasted with the cations of the nickel salt that is dissolved in the plating bath, combine with the hydrogen cations to form an acid, which, in turn, lowers the pH of the plating bath.

In the contin-uous plating process disclosed in the T almey and Crehan patent, the plating bath is regenerated continuous-ly by the addition thereto of soluble nickel-containing and hypophosphite-containing reagents, as well as an alkalizing reagent for pH control; which regeneration of the plating bath during the plating of the catalytic material maintains not only the desired nickel cation concentration and hypophosphite anion concentration, but also preserves the most advantageous pH of the plating bath to assure a high plating rate. The continuous nickel plating process and system disclosed in this patent involves a plating chamber and a reservoir; and in the arrangement the plating solution is circulated from the reservoir to the plating chamber and back to the reservoir, the plating solution being heated to a relatively high temperature slightly below the boiling point thereof after withdrawal from the reservoir and before introduction into the plating chamber, and the plating solution being cooled to a relatively low temperature weil below the boiling point thereof after withdrawal from rice the plating chamber and before return into the reservoir. Of course, the catalytic body or bodies are plated by immersion in theplating solution in the plating chamber, whi-le the plating solution is regenerated in the reservoir by the addition of the previously mentioned regagents thereto in the reservoir. The catalytic body is subsequently withdrawn from the plating solution in the plating chamber after a time interval corresponding to the thickness of the nickel plating thereon that is desired.

A number of suitable aqueous: chemical nickel plating baths of the nickel cation-hypophosphite anion type that may be employed in the continuous nickel plating system of the Talmey and Crehan patent are disclosed in U.S. Patent No. 2,658,841, granted on Nov. 10, 1953,

to Gregoire Gutzeit and Abraham Krieg, and in U.S.`

Patent No. 2,658,842, granted on Nov. 10, 1953, to Gregoire Gutzeit and Ernest J. Ramirez, and in the copending applications of Gregoire Gutzeit, Paul Talmey and Warren G. Lee, Ser. No. 478,492, filed Dec. 29, 1954, now Patent No. 2,935,425, granted May 3, 1960, Ser. No. 479,088, led Dec. 31, 1954, now Patent No. 2,822,293, granted Feb. 4, 1958 and Ser. No, 569,815, filed Mar. 6, 1956, now Patent No. 2,822,294, granted Feb. 4, 1958. ln the continuous plating system, the plating bath disclosed in the Gutzeit, Talmey and Lee applications are preferred, both from the standpoint of economy and of performance, and four typical examples of such aqueous plating baths are as follows:

BATH I Nickel ions (as nickel sulfate) m.p.l 0.08 Hypophosphite ions (as sodium hypophosphite) m.p.l t 0.230 Lactic acid rn.p.l 0.30 to 0.40 Lead ions (stabilizer) ppm. Pb++ l pH adjusted to 4.6 with NaOH.

BATH 1I Nickel ions (as nickel sulfate) m.p.l 0.07 to 0.08 Hypophosphite ions (as sodium hypophosphite) m.p.l- 0.225 Lactic acid m.p.l 0.30 to 0.40 Propionic acid m.p.l- 0.03 Lead ions (stabilizer) p.p.m. Pb++ 1 pH adjusted to 4.6 with NaOH.

BATH III Nickel ions (as nickel sulfate) m.p.l- 0.08 Hypophosphite ions (as sodium hypophosphite) m.p.l 0.225 Lactic acid m.p.l- 0.20 Succinic acid -rn.p.l-- 0.06 Lead ions (stabilizer) -p.p.m. Pb++- l pH adjusted to 4.6 with NaOH.

BATH IV Nickel ions (as nickel sulfate) 'm.p.l 0.07 Hypophosphite ions (as sodium hypophosphite) m.p.l 0.230 Malic acid m.p.l 0.06 Lactic acid m.p.l 0.20 Succinic acid m.p.l 0.20 Lead ions (stabilizer) pp rn. Pb++ l pH adjusted to 4.6 with NaOH.

ln addition, each of the Baths I, Il, HI and IV contains a high-temperature stable, chemically inert, wetting agent of any suitable type, and in these baths the function of the organic additives (malic acid, lactic acid, succinic acid and propionic acid) is three-fold, as they act as: (l) buffers; (2) exaltants (plating rate booste1's); (3) complexing agents (to prevent precipi- 3 tations of nickel phosphite at high concentrations of HPO3 ions).

Of these organic additives, lactic acid combines the three effects named, succinic and propionic acids function principally as exaltants, while malie acid functions mainly as a complexing agent.

In the formulation of any one of these plating baths, an aqueous solution is prepared of the ingredients named; the nickel cations may be derived from nickel sulfate, nickel chloride, etc., or various combinations thereof; the hypophosphite anions may be derived from sodium hypophosphite, potassium hypophosphite, etc., or various combinations thereof; the other additives are introduced into the bath normally as the acids, or as the soluble salts thereof, etc.; and the desired pH of the bath is established by the eventual introduction thereinto of an acid or a base, as required, sulfuric acid and sodium hydroxide being recommended as a matter of economy and simplicity.

In the compositions of the various plating baths, the terms cation, anion and ion, as employed, include the total quantity of the corresponding elements that are present in the plating bath, i.e., both the undissociated and dissociated material. In other words 100% dissociation is assumed when the terms noted are used in connection with molar ratios and concentrations in the plating bath.

In the operation of the continuous plating system disclosed in the Talmey and Crehan patent, the whole body of plating solution, as a matter of volume, is continuously circulated from the reservoir to the plating chamber and back to the reservoir to constitute `what may be termed a cycle of circulation; and continuous regeneration thereof is accomplished in the reservoir by the continuous introduction thereinto of the reagents previously mentioned. Now after the whole body of plating solution has been used in production plating in a plurality of cycles of circulation, with the required regeneration thereof, its content in phosphite anions builds-up to a point where even the presence of relatively large quantities of complexing agents (necessarily rather Weak complexing agents) cannot prevent the precipitation of nickel phosphite therein. This point is reached when the phosphite concentration attains 0.7 to 1.5 m.p.l., epending on the particular bath composition. The nickel phosphite precipitate in the plating solution forms a suspensoid whose semi-colloidal particles causes roughness of the plating on the `catalytic bodies undergoing the plating operation, and also act as nuclei for thermal catalytic decomposition of the Whole body of plating solution, i.e., the formation of black precipitate therethrough. When this point is reached, the Whole body of plating solution may be termed depleted and has to be replaced with a freshly prepared body of plating solution in order to continue satisfactory plating of the catalytic bodies in the plating chamber.

A depleted plating bath may have, for instance, the following approximate composition:

M.p.l. Nickel ions 0.070.08 Hypophosphite ions 022-024 Phosphite ions 0.70-l.50 Sulphate ions 0.65-070 I actic ions 0.20-0.40

Sodium ions, q s.

Typical examples of a few depleted plating baths of the type previously described were found to have the following compositions:

DEPLETED BATH 'IA M.p.l. Ni ions 0.07

NaH2PO2 0.22 Na2HPO3 Lactic acid 0.30

DEPLETED BATH IIA Ni ions 0.07

NaHZPOZ Ntnrlro3 0.80 Lactic acid 0.30

Propionic acid 0.03

DEPLETED BATH IIIA Ni ions 0.084 NaH2PO2 0.201 NazHPO3 0.671 Lactic acid 0.20

Succinic acid 0.06

DEPLETED BATH IVA Ni ions 0.068

NaHZPOz 0.225 N212HPO3 Malic acid 0.06

Lactic-acid 0.2025

Succinic acid 0.20

DEPLETED BATH IVB Ni ions 0.07

NaH2PO2 0.20 Na2HPO3 0.86 Malic acid 0.06

Ilactic acid 0.20

Succinic acid 0.20

While the regeneration of the plating solution in the continuous plating process as disclosed in the Talmey and Creh'an patent, and involving the continuous addition thereto of the reagents mentioned, contributes very substantially to economical industrial plating operation, it is apparent that this regeneration of the plating solution does not proceed as far as is desirable in order to achieve maximum economy, since it will lbe observed from the compositions of the foregoing depleted plating baths that there are substantial values therein that might be further utilized.

Accordingly, it is another object of the invention to provide a continuous chemical nickel plating process of the character described that involves regeneration of the 'plating baths, not 'only by the addition thereto of nickel-containing and hypophosphite-containing `and alkalizing reagents, but also by the removal therefrom of phosphite ions, whereby depleted plating baths may be restored for further use.

A further object of the invention is to provide an improved process of restoring a depleted chemical nickel plating `bath so that it may `be employed for further use in the plating of catalytic bodies, which involves not only the removal of phosphite ions therefrom, but also the removal of other ions that have been `built-up therein as a consequence of the additions thereto of the reagents named.

A still further object of the invention lis to provide an improved process of restoring a depleted chemical nickel plating bath so that it may be employed for further use in the plating of catalytic bodies, which does not introduce any substantial foreign ions thereinto and Which effects the recovery of the valuable nickel cations, hypophosphite anions and organic additives therein.

The present invention is predicated upon the discovery that a depleted chemical nickel plating bath may be restored for `further satisfactory use in a continuous chemical nickel plating system of the character described, by proper treatment of the depleted plating `bath to remove therefrom phosphite anions land other ions that have been built-up therein by the addition of the make-up reagents, Without the introduction of foreign ions, so that the resulting aqueous solution fundamentally containing nickel cations, hypophosphite anions and organic additives may then lbe directly restored merely `by adding thereto nickelcontaining, hypophosphite-containing and acidifying or alkalizing reagents.

Still further features of the invention pertain to the particular arrangement of the steps of the process, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and principle of operation, together with further objects and advantages thereof, will 'best be understood by reference to the following specication taken in connection with the accompanying drawing, in which the single figure is a diagrammatic illustration of a continuous nickel plating system in which the process of the present invention may be carried out.

Referring now to the drawing, the continuous chemical nickel plating system there illustrated, and suitable for the carrying out of the present process, is essentially of the arrangement disclosed in the Talmey and Crehan patent. More particularly, the system fundamentally comprises a first reservoir 11a, a second reservoir 11b, a plating tank or chamber 12, a condenser 13, a primary vacuum flash .tank 14, a secondary vacuum flash tank 15, a primary steam jet pump 16, a secondary steam jet pump 17, and a mechanical pump 18. The reservoir 11a includes a baffled storage compartment 19a and a communicating regeneration compartment 20a; while the reservoir 11b includes a bamed storage compartment 191; and a communieating regeneration compartment 20h. In the arrangement, the inlet of the pump 18 selectively communicates with the upper and lower portions of the storage compartments 19a and 19b via respectively associated control valves 21a-22a and 2lb-22h; and the outlet of the pump 18 communicates with the upper portion of the condenser 13. The lower portion of the condenser 13 communicates with the upper portion of the plating tank 12; and the lower portion of the plating tank 12 communicates with the upper portion of the primary vacuum flash tank 14. The lower portion of the primary vacuum flash tank 14 communicates with the upper portionrof the secondary vacuum flash tank 15; and the lower portion of the secondary vacuum ash tank 15 selectively communicates with the upper portions of the regeneration compartments a and 2019 via respectively associated control valves 23a and 2311. Also, the upper portion of the primary vacuum ash tank 14 communicates with the primary steam jet pump 16, that is also connected to an associated source of high-pressure steam, not shown; and the discharge from the primary steam jet pump 16 communicates with the upper portion of the condenser 13. Also, the upper portion of the secondary vacuum flash tank 15 communicates with the secondary steam jet pump 17, that is also connected to the associated source of highpressure steam, not shown; and the discharge from the secondary steam jet pump 17 communicates with the atmosphere. This system contains an aqueous chemical plating solution of the character previously described; whereby a first portion of the plating solution is stored in one of the reservoirs 11a or 11b at a relatively low temperature well vbelow the boiling point thereof and in a relatively concentrated form;` while a second portion of the plating solution is held as a bath in the plating tank or chamber 12 at a relatively high temperature slightly below the boiling point thereof and in a relatively dilute form.

In the `operation of the system, the plating solution in the storage compartment 19a or 19h may have a tem perature of about 150 F.; while the plating solution in the plating tank 12 may have a temperature of about 210 F. The plating solution is circulated from the upper portion of the storage compartment 19a or 19b (depending upon which `of the control valves 21a or 2lb occupies its open position) by the pump 18 into the upper portion of the condenser 13, wherein it is both heated to the required temperature of about 210 F. and diluted to the required concentration by the discharge from the primary steam jet pump 16. The dilution of the plating solution in the condenser 13 is achieved not only by the introduction of the steam thereinto, but also by the introduction of the water vapor thereinto that is withdrawn from the upper portion of the primary vacuum flash tank 14 by the primary steam jet pump 16. The plating solution from the condenser 13 is circulated into the plating tank tank 12 and thence into the upper portion of the prima-ry vacuum flash tank 14 and therefrom into the upper portion of the secondary vacuum flash tank 15, and ultimately back into the upper portion of the regeneration compartment 20a or ,'Ztrb (depending upon which of the control valves 23a or 23b occupies its open position). In the primary vacuum flash tank 14, a vacuum of about l2 Hg is drawn by the primary steam jet pump 16; whereby water vapor is withdrawn from the` contained plating solution, as previously noted, so that the plating solution in the primary vacuum flash tank 14 is both coneentrated and cooled prior to introduction into the secondary vacuum flash tank 15. In the secondary vacuum flash tank 15, a vacuum of about 22 Hg is drawn by the secondary steam jet pump 17; whereby water vapor is withdrawn from the contained plating solution, so that the plating solution in the secondary vacuum flash tank 15 is both further concentrated and cooled prior to the return thereof to the regeneration compartment 29a or 2Gb. The plating solution returned into the regeneration compartment 20a or 2Gb may have a temperature of about F., as previously noted, as a consequence of the tandem cooling effects produced in the primary vacuum ash tank 14 and in the secondary vacuum ash tank 15. Also, the plating solution thus returned to the regeneration compartment 20a. or 20h is in the relatively Concen* trated form, as previously noted, as a consequence of the tandem concentrating effects produced in the primary vacuum flash tank 14 and in the secondary vacuum flash tank 15. Since the discharge of the secondary steam jet pump 17 is to the atmosphere, the: water vapor withdrawn from the plating solution in the upper portion ofv the secondary vacuum flash tank 15 prevents the build-up of water in the circulated plating solution; and preferably, the weight of the steam introduced into the plating solution in the condenser 13 by the primary steam jet pump 16 substantially equals the weight of the water vapor withdrawn therefrom in the secondary vacuum flash tank 15 and discharged to the atmosphere by the secondary steam jet pump 17, thereby maintaining the desired `balance of the weight of water supplied to and the weight of water extracted from the circulated plating solution.

The catalytic bodies are immersed in the plating bath in the plating chamber 12, whereby the metallic nickel (actually an alloy of nickel and phosphorous having a composition of about 89% to 97% nickel and 11% to 3% phosphorous by weight) is deposited upon the surfaces thereof; and the bodies are withdrawn from the plating bath when the coatings thereon are of the desired thickness. Incident to the plating of the nickel upon the catalytic bodies, the initial composition of the plating bath is altered by the reduction of the nickel cations and the oxidation of the hypophosphite anions, as previously noted, and the initial pH of the bath is reduced, as previously explained; whereby it is necessary to regenerate the plating solution in the regeneration compartment 20a or 2Gb by the addition thereto of an alkalizing reagent to restore the initial pH thereof and of a soluble nickel salt and a soluble hypophosphite to restore the initial composition thereof with respect to nickely cations and hypophosphite anions, the reagents mentioned being supplied into the regeneration compartment 29a or 2Gb, and

eing thoroughly dissolved and mixed thereinto before circulation back into the communicating storage compartment 19a or 19h.

Further, the system comprises make-up equipment 30 that -may include ve tanks 31 to 35, inclusive, that selectively communicate with make-up conduits 36 and 37 communicating with the regeneration compartments 20a and Ztlb. More particularly, the tanks 31 to 35, inclusive, may be selectively connected to the conduit 36 via respective control valves 41 to 45, inclusive, and the tanks 31 to 35, inclusive, may be selectively connected to the conduit 37 via respective control valves 51 to 55, inclusive. As a matter of convenience, the added alkalizing reagent may be derived from an aqueous sodium hydroxide stock solution stored in the tank 31, the added nickel reagent may be derived from an aqueous nickel sulfate stock solution stored in the tank 32, the added hypophosphite reagent may be derived from an aqueous sodium hypophosphite stock solution stored in the tank 33, water may be stored in the tank 34, and an aqueous sulfuric acid stock solution may be stored in the tank 35. It will be understood that the valves 41, 42, 43 and 44 are appropriately manipulated in order to bring about the required addition of the reagents from the tanks 31, 327 33 and 34 into the regeneration compartment 20a, while the valves 51, 52, 53 and 54 are appropriately manipulated in order to bring about the required addition of the reagents from the tanks 31, 32, 33 and 34 into the regeneration compartment 20h.

Finally, the system comprises apparatus 60 that is employed, as explained more fully hereinafter, for the removal of ,phosphite and other ions, the inlet to the apparatus 60 being selectively connected to the lower portion of the secondary vacuum flash tank via an associated control valve 61, and the outlet from the apparatus 60 being selectively connected to the regeneration compartments a and 20h via respective control valves 62a and 6211.

As a matter of -operating procedure, the plating solution may be continuously circulated from one of the reservoirs (for example, the reservoir 11a) to the plating tank 21 and back to the one reservoir 11a; and the plating solution may be continuously regenerated in the regeneration compartment 20a by the `continuous addition of the reagents thereto by proper manipulation of the control valves 41, 42, 43 and 44. Of course, this regeneration of the plating solution only restores the composition thereof with respect to nickel cations, hypophosphite anions and pH, but does not restore the initial composition thereof with respect to the ions that are :built-up therein, both by the plating reactions and by the additions of the reagents mentioned. In other words, as the plating solution is used in the plating operation, phosphite anions build-up therein, and likewise in the supply of make-up reagents thereto both sodium cations and sulfate anions are built-up therein (assuming that the stock solutions employed comprise nickel sulfate and sodium hypophosphite, as previously mentioned).

Accordingly, after predetermined utilization of the plating solution in the continuous plating system and continuous regeneration thereof with respect to the supply of make-up reagents thereto, it is necessary to effect a regeneration of the plating solution by the utilization of the 4apparatus 60 so as to bring about the removal from the plating solution of the phosphite removal from the plating solution of the phosphite anions, as well as the sodium cations and the sulfate anions. At this time, the control valve 23a is closed and the control valves 61 and 621; are opened, and operation of the apparatus `60 is initiated, as explained more fully hereinafter; whereby the plating solution from the lower portion of the secondary vacuum flash tank 15 is circulated through the apparatus 60 and thence into the regeneration compartment 20h o-f the reservoir 11b. At this time, the control valves 52, 53, 54 and 55 are appropriately controlled in order to cause the supply of the required make-up reagents into the regeneration compartment 20b so :as substantially completely to restore the initial composition of the chemical plating solution. In order to accommodate the complete removal of the depleted plating solution from the reservoir 11a, the control valve 22a is opened to place the lower portion of the reservoir 11a into communication with the inlet of the numb 18.

In view of the foregoing, it will be understood that the depleted plating solution is circulated from the reservoir 11a through the plating tank 12 and thence into the apparatus 60 and then into the reservoir 11b. Subsequent- 1y the restored plating solution is circulated from the reservoir 11b through the plating tank 12 and thence back into the regeneration compartment Zflb of the reservoir 11b, the control valves 61, 23a and 22b being operated into their closed positions and the control valves 23h and 2lb being operated into their open positions at this time, whereby operation of the apparatus 60 may be arrested.

In view of the foregoing description of the mode of operation of the continuous plating system, it will be understood that as the plating solution is circulated from the reservoir 11a through the plating chamber 12, it is continuously regenerated by the addition thereto of nickel cations, hypophosphite anions and hydroxyl anions, employing the make-up equipment 30; and after a predetermined utilization thereof, it becomes necessary to regenerate it by the removal therefrom of phosphite anions, sodium cations and sulfate anions, employing the apparatus 60, followed by the addition thereto of nickel cations, hypophosphite anions and hydrogen cations, employing the make-up equipment 30. This predetermined utilization and consequent depletion of the plating solution is manifest by the build-up therein of a phosphite anion concentration within the approximate range 0.7 to 1.5 m.p.l., and is normally reached when the accumulative nickel salt addition is such that about 400% to 500% nickel cations (with respect to the initial nickel cation content of the plating solution) have been addedV thereto in the continuous regeneration thereof, employing the make-up equipment 30.

Considering now in greater detail the matter of the removal of the phosphite anions, together with the sodium cations and the sulfate anions, from a depleted plating bath in the apparatus 60, it is noted that any one of a number of individual treatments, described more fully hereinafter, may be employed. In the treatment, the desirable values contained in the depleted plating baths are recovered and the resulting aqueous solution is reconstituted to provide the restored plating solution. In the treatment, it is desirable rst to remove from the depleted plating solution, the contained nickel cations, and this may be best done by any such conventional step which does not introduce foreign ions into the solution; i.e., electrolysis or cations exchange. Early elimination of the nickel cations is highly desirable because a variation of the pH of the solution due to reagent additions will induce a modification of the chelate stability and will result in nickel phosphite precipitation. Nickel phosphite is difficult to lter; and moreover, in order to recover the nickel, it has to be dissolved in acid and treated, which represents an additional step. Ion exchange is preferred for the nickel cation recovery over electrolysis because the latter results in an anodic oxidation of hypophosphite to phosphite. For example, a column packed with the cation exchange resin sold by Rohm and Haas under the name Amberlite IR- is quite satisfactory for the present purpose; and likewise, the cation exchange resin sold by Dow under the name Dowex 50 is entirely satisfactory.

A cation exchange resin of the type specified is ordinarily of bead-like formation and essentially comprises a stable insoluble synthetic organic polymer, active acidic functional groups chemically bonded thereto and dissociable into free mobile hydrogen cations to impart a negative charge to the polymer, and water in gel relationship with the polymer. The active acidic functional groups attached to the associated organic polymer are oriented with respect to the interfaces thereof so as to be partially or completely dssociable in the internal gel water into fixed negative ions linked to the polymer and into mobile exchangeable hydrogen cations. Typical polymers to which active acidic functional groups may be attached include: phenolaldehyde resins, polystyrene-divinylbenzene copolymers,

and the like; and such suitable acidic functional groups include: -SO3H, -COOH, and the like. Normally, the water in gel relationship with the polymers should be present in the amount of at least 15% of the weight of the dry resin.

In the subsequent treatment, it is the primary object to remove a major portion of the phosphite anions, leaving, if possible, all the other constituents of the solution unchanged. Also in the treatment, it is the secondary object to remove at least a portion of the sodium cations and the sulfate anions in order to keep these ions between certain limits, i.e., at an appropriate predetermined level so as to avoid any substantial build-up thereof. In order to eliminate economically the phosphite anions, a cheap reagent has to be used, the cationsof which form a phosphite compound that is less soluble than nickel phosphite, and the anions of which are identical to one of the anions already contained in the depleted solution. Moreover, this cation of the reagent mentioned cannot be a catalytic poison for the chemical nickel plating reaction (such as cadmium). Finally, the organic additives (lactic acid, etc.) contained in the solution should form soluble salts with the cation of the reagent mentioned. The last mentioned requirement leads to a preference of Baths I and 1I in the continuous nickel plating process, since the salts of lactic acid an'd'propionic acid with alkaline earth metals, and also with most heavy metals, are highly wawith cold water, whereby it consists essentially of cal-,

cium phosphite, containing a small amount of calcium sulfate. The filtrate is then cooled to a relatively low temperature, about 0-5 C., while bubbling therethrough a small amount of carbon dioxide throughout a time interval of about thirty minutes, effecting the crystallization of sodium sulfate therein and the precipitation of calcium carbonate therein, The resulting solution is then filtered, whereby the filter cake is predominantly sodium sulfate containing small amounts of calcium carbonate, sodium carbonate and sodium bicarbonate. The resulting filtrate comprises the base of a restored plating solution, since it contains substantial hypophosphite anions, as well as the organic additives (lactic acid, etc.). More particularly, to the resulting filtrate there are added nickel sulfate and sodium hypophosphite, as Well las a small amount of stabilizer (such as 1 3 ppm. of lead ion); and then the pH of the solution is adjusted to the required value (normally about 4.6) by the addition of sulfuric acid or sodium hydroxide, if required. At this time, the `reconstituted or restored plating solution is ready for use in the continuous nickel plating system.

Speciiically,` to the eliluent mentioned the calcium hydroxide may be added in the form of an aqueous slurry and the resulting mixture is filtered to produce the corresponding filtrate. 4

The chemical reactions involved in this basic treatment of the depleted plating solution are as follows:

The reactions involved in the treatment of a depleted plating bath, in the manner described above, Will be readily understood from the following ow sheet:

metingen Depleted Bath IIB o .o7 o .oe

(Herog) 0.22 o .24

(HPO3V 0.75 o .eo

S04" O .60 O .70

Ca++ none Lactc acid O .30

Propionic acid 0.05

Cation il l2 Effluent L N++ none (312202)" 0 .22 0.24 -mpl (HP03V 0.75 0.80 mp1 S04 O .60 O .'70 mp1 Ca++ none La ctic acid O .50 mp1 Proponic acid 0.05 mp1 Effluent Filtrate I (above) Add: Ca(OH)2 Ni++ none (HZPOQV O .2O O .24 mp1 (111305)" O .O7 0.15 mp1 S04" 0 .60 0.70 mp1 Laotic acid. 0.50 mp1 Proponic acid O O5 mp1 Filter Cake I V Ni++ none Filtrate I Filtrate II i i (above) Cool to Ni++ None 0o 50C and d" (H2202) O .19 0.24 mp1 add C02` (HP05)" O .O5 0.15 mp1 sof 0.111r 0.24 mp1 Ca++' t none 0 .O05 mp1 t tactic Y l acid A 1 O '3:03 5 mp1 Propiouc f i v A acid 0.05 mp1 lliziltseic' Cake II Ni'H' i none (HZPOZ) 0.1%y '(HroBV' 0.5%

Dry Basis S04 i 64.2% A..Nai' 28 5% Subject to Elution t. Caton Exchange Resin f with HZSOL1F N Eluaise` Nid-d- Combine Filtrate II (above) with eluate (above); and and 10% ofthe malic ions are removed as the correspondthen reconstitute by addition of nickel-sulfate- -or' nickel ing-calcium salts in Filter Cake 1I; whereby, when Filtrate carbonate or nickel hydroxide, hypophosphorus acid, sta- II is subsequently reconstituted, it is necessary to add bilizer (1-3 ppm. Pb++) and adjust pH to 4.6 with 70 corresponding amounts of succinic acid and malic acid. NaOH so as to provide the restored plating bath. In order to demonstrate the practical value of the When the treatment procedure of Flow Sheet I is present treatment, a depleted plating Bath IVA was applied to a depleted plating bath containing succinic reconstituted to produce restored plating Bath 1V in acid and malic acid as organic additives, such, for exaccordance with the procedure of Flow Sheet I; and ample, as Bath IV, approximately 10% ofthe succinic ions 75 then a continuous plating run was made in the continuous l5 plating system described utilizing this restored plating bath, with the following results:

Cycle Number 1 2 3 4 Total Weight gain 23. 97 45.25 40. 97 30. 50 Plating rate X104 (grn./cm.2/min.).. 3.33 3.14 3. 56 3. 53 Plating rate (mils/hr.) 0. 899 0. 849 O. 960 0. 953 Plating time (min.) 225 450 360 270 Appearance (l) (1) (l) 1 Smooth and bright.

Y Depleted Bath In this plating run, appropriately cleaned steel samples were nickel plated in the four cycles set forth, the nickel plating upon the samples being smooth and bright and entirely satisfactory.

In a modified, but less desirable, form of this treatment of the depleted plating bath, the nickel cations therein are not removed by ion exchange prior to the precipitation of the phosphite; and employing calcium hydroxide, both calcium phosphite and nickel phosphite are precipitated and removed from the resulting solution in the iirst lter cake. This modified procedure will be readily understood from the following ow sheet:

FLOW SHEET IM IIB Filtrate I Ni++ 0.07 0.08 mp1 Ni++ none (812202)" 0.22 0.24r mp1 (H2P02V 0.20 0.24 mp1 (18205)" 0.75 0.80 mp1 Ada: (11205)" 0.07 0.15 mp1 S04" 0.60 0 .70 mp1 cama)2 804' 0.60 0.70 mp1 Ca++ none 7 Ca++ 0.7 1.6 mp1 Laetic acid 0.30 mp1 Lactc acid 0.30 mp1 Iropionc acid O .O5 mp1 Propionio acid 0.05 mp1 vFilter' Cake I Y Ni++ 2 .0 2 .5% (H'oz 0.57- 0.4475 g -U Dry Basis (H1205) 30 .0 -58 .0%

Flbaife I Filtrate II (above) 0001 'bo O5OC Hft'F none (nienr 0.05 0.13' mp1 S04 0.14 0.24- mp1 Ca'H' none 1:0 0.005 mp1 Lactic acid O .50 mp1 Proponc 4 acid 0.05 mp1 Filter Cake II y Ni'H" l none )l i (HZPOZV 0.1% g (m05) 0.5% I i A Dry S04."` 54 2% t' t Basis Na+ 2e 53 .5%

0J* i 2 .4%q 1 Reconstitute Filtrate II above by the addition of nickel subjected to elusion with sulfuric acid, the eluate consulfate, etc., hypophosphorus acid, stabilizer (1-3 p.p.m. taining Ni++ and SO4 which eluate may be employed PbLJf) and adjust PH t0 4'6 With NaOH S0 3S t0 Provide in conjunction with the reconstitution of Filtrate II, in the restored Plating bath' the manner previously explained.

In `conjunction with Flow Sheet IM, it is pointed out 70 In a modied form of the treatment of the depleted that the nickel contained in Filter Cake I may be rel t. y 1 t. th k1 t. nr t m d covered by dissolving the latter in sulfuric acid and then p a mg so u lon e mc e Ca lons are s re Ove subjecting the resulting Solution to ion exchange em therefrom by cation exchange; and to the effluent, barium ploying acation exchange resin of the character previously hydfOXlde 1S added 1n Slight. excess 0Ver the theoletlcal specied. Thereafter, the cation exchange resin may be 75 amount required to precipitate the phosphite anions present in the solution. Specifically, to the eiuent mentioned produce the corresponding filtrate. This modified prothe barium hydroxide may be added in the `form of an cedure Will be .readily understood from the following aqueous slurry and the resulting mixture is filtered to flow sheet:

FLOW SHEET II Depleted Bath IV C Cation Exchange Resin NiCl2 0.068 mp1 Ni++ NaHQPO2 O .225 mp1 Contact Caton Na2HPO5 f O .74 mp1 Exchange Resln Malic acid O .O6 mp1 Lactie acid O .2025 mp1 Succinc acid 0.20 mp1 Effluent I l Ni++ none NallbO2 0.225 mp1 Na2HPO5 0.74 mp1 Malc acid 0.06 mp1 Ilactc acid 0.2025 mp1 Succnic 0.20 mp1 acid Effluent Filtrate I (above) NaH21 o2 0.225 mp1 NaHPO5 0.071 mp1 Malic acid O .O5 mp1 Add:

Lectio acid O .2025 mp1 B21(OH)2 Succinic acid O .18 mp1 Ba'H' excess Filter Cake I laHlEO5 Ba. Malace Ba Succinate Filtrate I Filtrate Il Add: H so to (above) 2 4 NaH22o2 0.223 mp1 pH 6 .0; Agitate c Filter Na2HPO5 O .O71 mp1 Na2SO4 same Malic acid O .O3 mp1 Lectio acid O .2025 mpl Succinic acid O .18 mp1 Filter Cake II BaSO Subject Filtrate II above to the cooling and CO2 contact steps disclosed in Flow Sheet I in order to precipitate Na2SO4, etc., and lter to produce Filter Cake III con- 75 NaZSO4).

sisting fundamentally of NaZSO; and Filtrate III corresponding to Filtrate Il above (after the removal of Then reconstitute Filtrate III mentioned above by the addition thereto of nickel chloride, malic acid, succinic acid, and adjust the pH to 4.6` with NaOH so as to provide the restored plating bath,

In conjunction with Flow Sheet II, it will be observed that substantially all barium ions in Filtrate I are removed therefrom by the .addition of sulfuric acid bringing about the precipitation of barium sulfate.

Just as the treatment of Flow Sheet I was modified to produce Flow Sheet IM, as explained above, Flow Sheet II may be modified to produce a corresponding Flow Sheet IIM. In this modified treatment of the depleted plating bath, the nickel cations therein are not removed by the ion exchange prior to the precipitation of the phosphite, and when the barium hydroxide is added to the depleted plating bath, both barium phosphite and nickel phosphite are precipitated and removed from the resulting solution in the first filter cake. This modied procedure is not set forth in further detail in the interest of brevity.

In another modified form of the treatment of the depleted plating solution, the nickel cations are first removed therefrom by cation exchange; and to the effluent, magnesium carbonate is added in slight excess over the theoretical amount required to precipitate the phosphite anions present in the solution. Specifically, to the eliiuent mentioned the magnesium carbonate may be added in the forrn of a powder or an aqueous slurry and the resulting mixture is filtered to produce the -corresponding ltrate. This modified procedure will be readily understood from the following flow sheet:

gygy SHEET III Depleted Bath IV B Niwr o .o7 mp1 NaH21 o2 0.20 mp1 Na2HPO5 0.86 mp1 Malc acid 0.06 mp1 Lactic acid O .20 mp1 Suocinc 0.20 mp1 acid Cation Exchange Resin Contact Cabion Exchange Resin 25 26 Effluent Filtrate I (above) sangre2 0.20 mp1 Na2lil03 0.15 mp1 Malia acid 0.05 mp1 Add:

Lactic acid 0.20 mp1 Mgco5 Succinc acid 0.20 mp1 Mg++ 0.1 mp1 Filter Cake I Malic acid Subject Filtrate I above to the cooling and CO2 contact steps disclosed in Flow Sheet I in order to precipitate Na2SO4, etc.; and lter to produce Filter Cake II consisting fundamentally of Na2SO4 and Filtrate II corresponding to Filtrate I above (after the removal of Nazsoil).

Then reconstitute Filtrate II mentioned above by the addition thereto of nickel sulfate, sodium hypophosphite, malic acid and stabilizer (l-3 ppm. Pbti'), and adjust pH to 4.6 with NaOH so as to provide the restored plating bath.

In conjunction with Flow Sheet III, it is noted that small amounts of magnesium cations are introduced into Filtrate I that are carried into the ultimately reconstituted or restored plating bath. Further, it will be appreciated that in addition to precipitating the phosphite anions as magnesiuni phosphite, by metastatic exchange, the magnesium carbonate also removes phosphite and some hypophosphite and sulfate anions by adsorption in Filter Cake I, as magnesium carbonate is an anion adsorption material with respect lto these anions. However, the magnesium carbonate carries into Filter Cake I `by adsorption no substantial proportion of malic, lactic or succinic anions, or other weakly acidic bath constituents. Moreover, the reconstitution of Filtrate II may involve the addition of nickel carbonate or nickel hydroxide and the addition of hypophosphorus acid, as explained in connection with Flow Sheet I above. Of course, it will be understood, that the utilization of nickel carbonate and nickel hydroxide in the reconstitution of Filtrate II also increases the pH thereof, whereby it may be necessary to add an acid (H2804) to Filtrate II to obtain the desired pH of about 4.6 ofthe reconstituted plating bath.

Just as -the treatment of Flow Sheet I was modified to produce Flow Sheet IM, as explained above, Flow Sheet III may be modified to produce a corresponding Flow Sheet IHM. In this modified treatment of the depleted plating bath, the nickel cations therein are not removed by ion exchange prior to `the precipitation of the phosphites, and when the magnesium carbonate is added to the depleted plating bath, both magnesium phosphite and nickel phosphite are precipitated and removed from the resulting solution in the rst lter cake. This: modied procedure is not set forth in further detail in the interest of brevity.

In the foregoing treatment procedures, the depleted plaiting baths were restored substantially to the initial compositions thereof by the complete removal of substantially all of the phosphite and other foreign ions, together with the additions of the nickel cations and the hypophosphite anions; however, substantial advantages and economies may be achieved in the continuous process of chemical nickel process by utilizing more simplified procedures that do not necessarily restore the depleted plating bath to its initial composition, :but that do remove phosphite anions therefrom and supply nickel cations and hypophosphite anions thereto.

For example, a depleted plating bath of any one of the types previously mentioned may be restored to its approximate initial composition in a simple and ready manner by adding thereto a suitable quantity of nickel hypophosphite, nickel sulfate, nickel carbonate, nickel hydroxide, or other nickel salt, and a suitable quantity of nickel hypophosphite, sodium hypophosphite, hypophosphorus acid, or other hypophosphite, followed by contacting the resulting solution with freshly precipitated or active aluminum hydroxide. Specifically, the freshly precipitated AMOI-D3 may be added and stirred into the solution, while heating the same, for about one hour. Thereafter, the resulting slurry is ltered and the pH ofthe ltrate is adjusted with a suitable acid to producea restored plating bath. This arrangement is very advantageous as the freshly precipitated or active A1(OH)3 comprises an anion adsorption material for phosphite and sulfate anions, as well as to some extent `for hypophosphite anions, but the required amount of hypophos-phite anions may be added to compensate for this efect; whereby the undesirable phosphite and sulfate an- 27 ions are removed Ifrom the depleted plating bath. This arrangement is very simple, introduces no foreign ions into the resulting restored plating bath, and can be carried out with substantially no chemical controls, after the initial procedure is established. Moreover, the arrangement meets all of the fundamental requirements of regeneration as it supplies needed nickel cations and hypophosphite anions and removes undesirable phosphite and sulfate anions.

In order to demonstrate lthis procedure, a plating bath was initially composed comprising:

NiSO4 m.p.l 0.1125 NaH2PO2 m.p.l 0.225 NH2CH2COOH m.p.l 0.180 NaOH m.p.l 0.1'20 pH 6.48

With this plating solution, properly cleaned steel samples were plated in a plating chamber having a volume of about 300 cc. employing 2000 cc. of the plating solution, the plating solution being continuously flowed through the plating chamber at a rate of about 50 cc. per minute and the temperature thereof in the plating chamber being maintained at about 96 to 97 C. In this plating test 0.6807 gm. of bright smooth plating was produced upon the steel samples, whereby the plating rate was 4. 34 10'4 lgm./icm.2/min. The time of the test was 40i minutes; the solution remained clear in the test; and the pH thereof was decreased from 6.48 to 6.01.

Thereafter the plating solution was partially regenerated by adding thereto 4.25 gms. of Ni(H2PO2)2; and to the solution a quantity of freshly precipitated A1(OH)3 was added and stirred therein for a time interval of one hour. The resulting slurry was lthen filtered and the pH of the filtrate was 6.5.

The filtrate mentioned was utilized directly as a regenerated plating solution and therewith properly cleaned steel samples were again plated in the plating chamber with 2060 cc. of the solution, the plating solution being continuously flowed through the plating chamber at a rate of about 53 cc. per minute, and the temperature thereof in the plating chamber being maintained at about 97 C. In this plating test 0.7674 gm. of bright smooth plating was produced upon the steel samples, whereby the plating rate was 5.00X-4 gm./cm.2/min. The time of the test was 39 minutes; the solution remained clear in the test; and the pH thereof was decreased from 6.50 to 6.13.

Thereafter the plating solution was again partially re-l generated by adding thereto 3.35 gms. of Ni(H2PO2)2; and to the solution a quantity of freshly precipitated A1(OH)3 was added and stirred therein for a time interval of one hour. The resulting slurry was then filtered and the pH ofthe filtrate was adjusted to 6.42.

The filtrate mentioned was utilized directly as a regenerated plating solution and therewith properly cleaned steel samples were again plated in the plating chamber with 2000 cc. of the solution, the plating solution being continuously fiowed through the plating chamber at a rate of about 57 cc. per minute and the temperature thereof in the plating chamber being maintained at about 96 C. In this plating test 0.7767 gm. of bright smooth plating was produced upon the steel samples, whereby the plating rate was 5.35 104 gm./cm.2/min. The time of the test was 35 minutes; the solution remained clear in the test; and the pH thereof was decreased from 6.42 to 6.15.

Thereafter the plating solution was again partially regenerated by adding thereto 3.64 gms. of Ni(H2PO2)2; and to the solution a quantity of freshly precipitated Al(OH)3 was added and stirred therein for a time interval of one hour. The resulting slurry was then filtered and the pH of the filtrate was adjusted to 6.39.

The filtrate mentioned was utilized directly as a regenerated plating solution and therewith properly cleaned steel samples were again plated in the plating chamber with 2000 cc. of the solution, the plating solution being continuously tiowed through the plating chamber at a rate of about 57 ce. per minute, and the temperature thereof in the plating chamber being maintained at about 97 C. In this plating test 0.7386 gm. of plating was produced upon the steel samples, whereby the plating rate was 5.37 1O4 gm./cm.2/min. The time of the test was 35 minutes; the solution remained clear in the test; and the pH thereof was decreased somewhat below 6.39.

Another approximate regeneration procedure was devised that is predicated upon regeneration with nickel hydroxide and hypophosphorous acid for the purpose of supplying the required nickel cations and hypophosphite anions, and upon utilization of the adsorption characteristic of the nickel hydroxide for the removal of undesirable pho-phite anions.

In accordance with this procedure, an initial aqueous slurry was prepared having the composition:

Ni(OH)2 mole 0.45 H3PO3 gms 10 NaCl gms 21.1 H3PO2 gms-- 79.2 Malonic acid gms 18.75 Dialite (filter aid) grns l 40.0 Tap water liters 2 The pH of the wet Ni(OH)2 as prepared was 8.23

The slurry was thoroughly agitated until the pH thereof became constant at about 6.30 after 7 hours of agitation. Then the slurry was filtered and 3200 cc. of filtrate was obtained having a pH of 6.35.

The filtrate was employed as a plating solution and therewith properly cleaned steel samples were plated in a plating chamber having a volume o-f about 300 cc. employing 3200 cc. of the plating solution, the plating solution being continuously flowed through the plating chamber at a rate of about 55 cc. per minute, and the temperature thereof in the plating chamber being maintained at about 98 C. In this plating test 1.2273 gms. of bright smooth plating was produced upon the steel samples, whereby the plating rate was 2.69)(10-4 gm./cm.2/min. The time of the test was 58 minutes; the solution remained clear in the test; and the pH thereof was decreased from 6.35 to 4.33.

Thereafter the plating solution was partially regenerated by adding the same back to the filter cake that was produced by the filtering of the initial slurry, the filter cakementioned having been ground into finely divided form, whereby a new slurry was produced after an addition of malonic acid and water, that had the following composition:

Ni(OH)2 m.p.l 0.3 NaCl m.p.l 0.24 HQPOZ m.p.l 0.227 H3PO3 m.p.l 0.0122 Malonic acid m.p.1 0.12 Filter aid (total) gms 40 Volume of slurry liters 4 This new slurry was thoroughly agitated until the pH thereof came to equilibrium at 6.19 after about 7 hours, whereupon the `same was filtered, the filtrate had a volume of 3400 cc. and a pH of 6.03. The pH of the filtrate was then adjusted to 5.42 with acid, and 3200 cc. thereof was employed as a plating bath, and therewith properly cleaned steel samples were plated in the plating chamber, the plating solution being continuously fiowed through the plating chamber at a rate of about 61.5 cc. per minute, and the temperature thereof in the plating chamber being maintained at about 98 C. In this plating test 0.7293 gms. of bright smooth plating was produced upon the steel samples, whereby the plating rate was 1.78 X10-4 gm./cm.2/min. The time of the test was 52 minutes; the solution remained clear in the test; and the pH thereof was decreased from 5.42 to 4.52.

In view of the foregoing, it will be understood that in the -continuous chemical nickel plating process, the effective or useful life of the initial plating solution may be greatly extended by the regeneration thereof, including the removal of the deleterious phosphite anions therefrom; and the treatment of Flow Sheet I is especially recommended in view of the circumstance that it is the most advantageous of all of the treatments disclosed with respect -to the removal from the plating solution of phosphite Ianions, sodium cations and sulfate anions, without the introduction theieinto of foreign ions, whereby the plating solution may be restored any number of times after a corresponding number of intervening depletions thereof.

In lthe foregoing description, periodic or intermittent regeneration of the plating solution, with respect to the lremoval of phosphite, anions, `sodium cations and sulfate anions, in the continuous plating system was explained; however, it will be understood that this regeneration of the plating solution in the system may be continuous. This may be accomplished in a ready manner by opening the control valves 6l and 62a (utilizing the reservoir 11a) so that the apparatus 6i) is arranged in by-passing relation with respect to the direct return of the plating solution to the regeneration compartment 20a. rl`he control valve 23a also being open at this time. Thus in this arrangement, two portions of the plating solution from the lower portion of the secondary vacuum fiash tank l respectively flow directly into the regeneration compartment a via the control valve 23a and indirectly into the regeneration compartment 26a via the control valve 6l `and the apparatus Gil. By treatment of the portion of the plating solution passing through the apparatus 6ft, in the manner previously explained, the required removal of phosphite anions, sodium cations and sulfate anions may be accomplished upon a continuous basis so as to prevent excessive depletion thereof in the continuous plating operation.

Accordingly, it will be understood that there has been provided a continuous chemical nickel plating process that is highly suitable for use on an industrial scale, that involves regeneration of the plating bath, 'as itbecomes depleted with use, in a simple manner, thereby rendering the plating bath of exceedingly long life and contributing to overall efciency of .the continuous chemical nickel plating process.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. In the continuous process of chemically plating with nickel a body of catalytic material that involves providing an aqueous plating solution of the nickel cation-hypophosphite anion type and having an initial composition including a pH in a first given range and a nickel cation concentration in a second given range and a hypophosphite anion concentration in a third given range, holding said solution in a plating chamber at a plating temperature disposed below the boiling point thereof but well above room temperature, immersing said body in said solution in said plating chamber to effect nickel plating on the surface thereof, and withdnawing said body from the portion of said solution in said plating chamber after a time interval corresponding to the thickness of the nickel plating on the surface of said body that is desired, said nickel plating of said body resulting from the reduction of nickel cations to metallic nickel with the corresponding oxidation of hypophosphite anions to phosphite anions, whereby during said time interval both nickel cations and hypophosphite anions are depleted and both hydrogen cations and phosphite anions are produced in said solution in said plating chamber, with the result that said solution in said plating chamber tends to depart substantially from said initial composition; the improvement comprising withdrawing during Said time interval a part of said solution from said plating chamber, treating during said time interval the withdrawn part of said solution to restore the same substantially to said initial composition, and returning during said time interval said restored par-t of said solution into said plating chamber, said treatment of the Withdrawn part of said solution including reacting the same with an alkaline earth hydroxide to precipitate a corresponding alkaline earth phosphite therein, separating the precipitated alkaline earth phosphite 'from the resulting solution, and adding to the resulting solution sufficient pH control ions to restore the pH thereof into said first range and sufficient nickel cations to restore the concentration thereof into said second range and sufficient hypophosphite anions to restore the concentration thereof into said third range.

2. In the continuous process of chemically plating with nickel a body of catalytic material that involves providing an aqueous plating solution of nickel sulfate and sodium hypophosphite and having an initial composition including a pH in a first given range and a nickel cation concentration in a second given range and a hypophospihte anion concentration in a third given range, holding said solution in a plating chamber at a plating temperature disposed below the boiling point thereof but well above room temperature, inimersing said body in said solution in said plating chamber to effect nickel plating on the vsur-face thereof, and withdrawing said body from said solution in said plating chamber after a time interval corresponding to the thickness of the nickel plating `on the surface of said body that is desired, said nickel plating of said body resulting Vfrom the reduction of nickel cations to metallic nickel with the corresponding oxidation of hypophosphite anions to phosphite anions, whereby Aduring said time interval both nickel cations and hypophosphite anions are depleted and both hydrogen cations and phosphite anions are produced in said solution in said plating chamber, with the result that said solution in said plating chamber tends to depart substantially from said initial composition; the improvement comprising withdrawing during said time interval a part of said solution from said plating chamber, treating during said time interval the withdrawn part of said solution to restore the same substantially to said initial composition, and returning during said time interval said restored part of said solution into said plating chamber, said treatment of the Withdrawn part of said solution including reacting the same with an alkaline earth hydroxide to precipitate la corresponding alkaline earth phosphite therein, separating the precipitated alkaline earth phosphite from the resulting solution, cooling the resulting solution to crystallize out sodium sul-fate therein, separating the crystallized sodium sulfate from the resulting solution, and adding to the resulting solution sufficient pH control ions to restore the pH thereof into said first range and sufiicient nickel sulfate to restore the nickel cation concentration thereof into said second range and sufiicient sodium hypophosphite to restore the hypophosphite anion concentration thereof into said third range.

3. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions and a given organic additive to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined. hypophosphite anion concentration and only some phosphite anions and substantially said given organic additive and having a given pH, which comprises contacting a mass of cation eX- chan ge material with said solution to remove nickel cations therefrom, -reacting the resulting solution With an alkaline earth hydroxide to precipitate a corresponding alkaline earth phosphite therein, separating the precipitated alkaline earth phosphite from the resulting solution, whereby the resulting solution contains only some nickel cations and some phosphite anions and considerable hypophosphite anions and substantially said given organic additive, and adding to the resulting solution sulicient nickel cations to obtain said predetermined nickel cation Iconcentration therein and sufficient 'hypophosphite anions to obtain said predetermined hypophosphite anion concentration therein Iand sucient pH control ions to obtain said given pH thereof.

4. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable sodium cations and considerable phosphite anions and considerable sulfate anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some sodium cations and only some phosphite anions and only some sulfate anions and having a given pH, which comprises contacting a mass of cation exchange material with said solution to remove nickel cations therefrom, reacting the resulting solution with an alkaline earth hydroxide to precipitate a corresponding alkaline earth phosphite therein, separating the precipitated alkaline earth phosphite from the resulting solution, cooling the resulting solution to crystallize out sodium sulfate therein, separating the crystallized sodium sulfate from the resulting solution, whereby the resulting solution contains only some nickel cations and some sodium cations and some phosphite anions and some sulfate anions and considerable hypophosphite anions, and adding to the resulting solution suf-cient nickel sulfate to obtain said predetermined nickel cation concentration therein and sucient sodium hypophosphite to obtain said predetermined hypophosphite anion concentration therein and suflicient pH control ions to obtain said given pH thereof.

5. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some phosphite anions and having a given pH, which comprises contacting a mass of cation exchange material with said solution to remove nickel cations therefrom, reacting the resulting solution with an alkaline earth hydroxide to precipitate a corresponding alkaline earth phosphite therein, separating the precipitated alkaline earth phosphite from 'the resulting solution, and adding to the resulting solution sufficient soluble nickel salt to obtain said predetermined nickel cation concentration therein and sucient soluble hypophosp-hite to obtain said predetermined hypophosphite anion concentration therein and sufcient pH control ions to obtain said given pH thereof.

6. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some phosphite anions and having a given pH, which comprises contacting a mass of cation exchange material with said solution to remove nickel cations therefrom, reacting the resulting solution with calcium hydroxide to precipitate calcium phosphite therein, separating the precipitated calcium phosphite from the resulting solution, and addin-g to the resulting solution sufficient soluble nickel salt to obtain said predetermined nickel cation concentration therein and sufficient soluble hypophosphite to obtain said predetermined hypophosphite anion concentration therein and suicient pH control ions to obtain said given pH thereof.

7. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable sodium cations and considerable phosphite anions and considerable sulfate anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some sodium cations and only some phosphite anions and only some sulfate anions and having a given pH, which comprises contacting a mass of cation exchange material with said solution to remove nickel cations therefrom, reacting the resulting solution with an alkaline earth hydroxide to precipitate a corresponding alkaline earth phosphite therein, separating the precipitated alkaline earth phosphite from the resulting solution, cooling the resulting solution to a temperature Within the approximate range 0 to 5 C. to crystallize out sodium sulfate therein, separating the crystallized sodium sulfate from the resulting solution, and adding to the resulting solution sufficient nickel `sulfate to obtain said predetermined nickel cation concentration therein and sufficient sodium hypophosphite to obtain said predetermined hypophosphite anion concentration therein and sufficient pH control ions to obtain said given pH thereof.

8. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable sodium cations and considerable phosphite anions and considerable sulfate anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some sodium cations and only some phosphite anions and only lsome sulfate anions and having a given pH, which comprises contacting a mass of cation exchange material with said solution to remove nickel cations therefrom, reacting the resulting solution with calcium hydroxide to precipitate calcium phosphite therein, separating the precipitated calcium phosphite from the resulting solution, cooling the resulting solution to a temperature within the approximate range 0 to 5 C. to crystallize out sodium sulfate therein and reacting the same with carbon dioxide to precipitate calcium carbonate therein, removing the crystallized sodium sulfate and the precipitated calcium carbonate from the resulting solution, and adding to the resulting solution suicient nickel sulfate to obtain said predetermined nickel cation concentration therein and sufcient sodium hypophosphite to obtain said predetermined hypophosphite anion concentration therein and suiicient pH control ions to obtain said given pH thereof.

9. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some phosphite anions and having a lgiven pH, which comprises contacting a mass of cation exchange resin with said depleted solution in order to effect the removal of nickel cations therefrom, reacting the resulting effluent with an alkaline earth hydroxide to precipitate a corresponding alkaline earth phosphite therein, separating the precipitated alkaline earth phosphite from the reacted solution, subjecting said mass of -cation exchange resin to elution with an acid, whereby the .eluate contains nickel cations removed from said mass of ion exchange resin, combining the reacted solution and the eluate, and adding to the combined solution sutcient soluble nickel salt to obtain said predetermined nickel cation concentration therein and sutcient soluble hypophosphite to obtain said predetermined hypophosphite anion concentration therein and sufficient pH control ions to obtain said given pH thereof.

10. The process of treating a depleted chemical nickel plating solution of the nickel cation-hypophosphite anion type also containing phosphite anions, said process comprising reacting said solution with an alkaline earth hydroxide to precipitate a corresponding alkaline earth phosphite therein, separating the precipitated alkaline earth phosphite lfrom the resulting solution, an-d adding to the resulting solution nickel cations and hypophosphite anions to produce a restored chemical nickel plating solution containing predetermined nickel cations and predetermined hypophosphite anions.

11. The process set forth in claim 1G', wherein said alkaline earth hydroxide is selected from the class consisting of barium hydroxide and calcium hydroxide.

12. The process of regenerating a depleted chemical nickel plating solution of the nickel cation-hypophosphite anion type also containing phosphite anions and so-dium cations and sulfate anions, said process comprising reacting said solution with an alkaline earth hydroxide to precipitate a corresponding alkaline earth phosphite therein, separating the precipitated alkaline earth phosphite from the resulting solution, cooling the resulting solution to a temperature in the approximate range to 5 C. to crystallize out sodium sulfate therein, separating the crystallized Sodium sulfate from the resulting solution, and then adding to the resulting solution both nickel sulfate and sodium hypophosphite to produce a restored chemical nickel plating solution containing predetermined nickel cations and predetermined hypophosphite anions.

13. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypohosphite ,anions and considerable phosphite anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some phosphite anions and having a given pH, which comprises reacting said depleted solution With an alkaline earth hydroxide to precipitate both nickel phosphite and a corresponding alkaline earth phosphite therein, separating the precipitated nickel phosphite and alkaline earth phosphite from the resulting solution, and adding to the resulting solution suticient soluble nickel salt to obtain said predetermined nickel cation `concentration therein and sucient soluble hypophosphite to obtain said predetermined hypophosphite anion concentration therein land sufficient pH control ions to obtain said given pH thereof.

14. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some phosphite anions and having a given pH, which comprises reacting said depleted solution with calcium hydroxide to precipitate both nickel phosphite and calcium phosphite therein, separating the precipitated nickel phosphite and calcium phosphite from the resulting solution, and adding to the resulting solution sufficient soluble nickel salt to obtain said predetermined nickel cation concentration therein and suflicient soluble hypophosphite to obtain said predetermined hypophosphite anion concentration therein and sufficient pH control ions to obtain said given pH thereof.

15'. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable sodium cations vand considerable phosphite anions and considerable sulfate anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some sodium cations and only some phosphite anions and only some sulfate anions and having a given pH, which comprises `reacting said depleted solution with an alkaline earth hydroxide to precipitate both-nickel phosphite and a corresponding alkaline earth phosphite therein, separating the precipitated nickel phosphite and alkaline earth phosphite from the resulting solution, cooling the resulting solution to a temperature Within the Vapproximate range 0 to 5 C. to crystallize out sodium sulfate therein, separating the crystallized sodium sulfate from the resulting solution, and adding to the resulting solution suiicient nickel sulfate to obtain said predetermined nickel cation concentration therein and suflicient sodium hypophosphite to obtain said predetermined hypophosphite anion concentration therein and suicient pH control ions to obtain said given pH thereof.

16. The process of regenerating a depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable sodium cations `and considerable phosphite anions and considerable sulfate anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration and only some sodium cations and only some phosphite anions and only some sulfate anions and having a given pH, which comprises reacting said depleted solution with calcium hydroxide to precipitate both nickel phosphite and calcium phosphite therein, separating the precipitated nickel phosphite and calcium phosphite from the resulting solution, cooling the resulting solution to a temperature within the approximate range 0 to 5 C. to crystallize out sodium sulfate therein and reacting the same with carbon dioxide to precipitate calcium carbonate therein, separating the sodium sulfate and calcium carbonate from the resulting solution, and adding to the resulting solution sufcient nickel sulfate to obtain said predetermined nickel cation concentration therein and suicient sodium hypophosphite to obtain said predetermined hypophosphite anion concentration therein and sufficient pH control ions to obtain said given pH thereof.

17. The process of regenerating a depleted Vaqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentration and a predetermined hypophosphite anion concentration land only some phosphite anions and having a given pH, which comprises contacting a mass of cation exchange material with said solution to remove nickel cations therefrom, reacting the resulting solution with barium hydroxide to precipitate barium phosphite therein, separating the precipitated barium phosphite from the resulting solution, reacting the resulting solution with sulfuric acid to precipitate barium sulfate therein, separating the precipitated barium sulfate from the resulting solution, and Aadding to the resulting solution suiiicient solublenickel salt to obtain said predetermined nickel cation concentration therein and suicient soluble hypophosphite to obtain said predetermined hypophosphite anion concentration therein and suicient pH control ions to obtain said given pH thereof.

18. The process of regenerating a `depleted aqueous chemical nickel plating solution containing substantial nickel cations and substantial hypophosphite anions and considerable phosphite anions to produce a restored aqueous chemical nickel plating solution containing a predetermined nickel cation concentrati-on and a predetermined hypophosphite anion concentration and only some phosphite anions and having a given pH, which comprises contacting a mass of cation exchange material with said solution to remove nickel cations therefrom, contacting the resulting solution with magnesium carbonate to remove phosphite anions therefrom, separating the resulting magnesium phosphite from the resulting solution, and

35 adding to the resulting solution sufficient soluble nickel salt to obtain said predetermined nickel cation concentration therein and sufficient soluble hypophosphite to obtain said predetermined hypophosphite anion concentration therein and sufficient pH control ions to obtain said given pH thereof.

19. In a chemical reduction nickel plating process utilizing an aqueous solution containing nickel cations and a hypophosphite reducing agent, the improvement which consists of dissolving in said solution a nickel compound, lthereby to prevent during the process undesirable depletion of nickel cations in said solution, reacting said solution with an alkaline earth hydroxide to yprecipitate a corresponding alkaline earth phosphite therein, and sepalrating said precipitated alkaline earth phosphite from said solution, thereby to prevent during the process undesirable build-up of phosphite anions in said solution.

20. The process set forth in claim 19, wherein said nickel compound is selected from the group consisting of nickel hydroxide and nickel carbonate.

21. In a chemical reduction nickel plating process utilizing a plating bath comprising an aqueous solution containing a water-soluble nickel salt and a hypophosphite reducing agent, the improvement which consists of replenishing the hypophosphite in said bath by addition of hypophosphorous acid, and treating said bath with an anion adsorption material to remove phosphite ions produced by said process, wherein said anion adsorption material comprises aluminum hydroxide.

22. A method of treating chemical reduction plating solutions, said method comprising passing said solution through an anion adsorption material capable of adsorbing phosphite ions from said solution, wherein said anion adsorption material comprises aluminum hydroxide, and adding a hypophosphite reducing Iagent to said solution.

23. The process of treating a depleted chemical nickel plating solution of the nickel cation-hypophosphite anion type also containing phosphite anions, said process comprising contacting a mass of anion adsorption -material with said solution to remove phosphite anions therefrom, wherein said anion adsorption material comprises aluminum hydroxide, and adding to the resulting solution nickel cations and hypophosphite anions.

References Cited OTHER REFERENCES Costa, Industrial and Engineering Chemistry, vol. 42, No. 2, February 1950 (pp. 308 to 311 relied on), copy available in Class ZIO-24.1.

Kunin, Ion Exchange Resins, 1950, Iohn Wiley & Sons, Inc., New York, pp. to 139 relied on, copy available in Div. 50.

Paulson, Plating, vol. 40, No. 9, September 1953, pp. 1005 to 1009 relied on, copy available in Class ZIO-24.1.

ALEXANDER H. BRODMERKEL, Primary Examiner.

RICHARD D. NEVIUS, Examiner.

R. BLANKE, R. S. KENDALL, D. I. ARNOLD,

Assistant Examiners. 

1. IN THE CONTINUOUS PROCESS OF CHEMICALLY PLATING WITH NICKEL A BODY OF CATALYTIC MATERIAL THAT INVOLVES PROVIDING AN AQUEOUS PLATING SOLUTION OF THE NICKEL CATION-HYPOPHOSPHITE ANION TYPE AND HAVING AN INITIAL COMPOSITION INCLUDING A PH IN A FIRST GIVEN RANGE AND A NICKEL CATION CONCENTRATION IN A SECOND GIVEN RANGE AND A HYPOPHOSPHITE ANION CONCENTRATION IN A THIRD GIVEN RANGE, HOLDING SAID SOLUTION IN A PLATING CHAMBER AT A PLATING TEMPERATURE DISPOSED BELOW THE BOILING POINT THEREOF BUT WELL ABOVE ROOM TEMPERATURE, IMMERSING SAID BODY IN SAID SOLUTION IN SAID PLATING CHAMBER TO EFFECT NICKEL PLATING ON THE SURFACE THEREOF, AND WITHDRAWING SAID BODY FROM THE PORTION OF SAID SOLUTION IN SAID PLATING CHAMBER AFTER A TIME INTERVAL CORRESPONDING TO THE THICKNESS OF THE NICKEL PLATING ON THE SURFACE OF SAID BODY THAT IS DESIRED, SAID NICKEL PLATING OF SAID BODY RESULTING FROM THE REDUCTION OF NICKEL CATIONS TO METALLIC NICKEL WITH THE CORRESPONDING OXIDATION OF HYPOPHOSPHITE ANIONS TO PHOSPHITE ANIONS, WHEREBY DURING SAID TIME INTERVAL BOTH NICKEL CATIONS AND HYPOPHOSPHITE ANIONS ARE DEPLETED AND BOTH HYDROGEN CATIONS AND PHOSPHITE ANIONS ARE PRODUCED IN SAID SOLUTION IN SAID PLATING CHAMBER, WITH THE RESULT THAT SAID SOLUTION IN SAID PLATING CHAMBER TENDS TO DEPART SUBSTANTIALLY FROM SAID INITIAL COMPOSITION; THE IMPROVEMENT COMPRISING WITHDRAWING DURING SAID TIME INTERVAL A PART OF SAID SOLUTION FROM SAID PLATING CHAMBER, TREATING DURING SAID TIME INTERVAL THE WITHDRAWN PART OF SAID SOLUTION TO RESTORE THE SAME SUBSTANTIALLY TO SAID INITIAL COMPOSITION, AND RETURNING DURING SAID TIME INTERVAL SAID RESTORED PART OF SAID SOLUTION INTO SAID PLATING CHAMBER, SAID TREATMENT OF THE WITHDRAWN PART OF SAID SOLUTION IN- 